Projectile



Jan. 17 1961 H. F. DUNLAP ETAL 2,963,246

' PROJECTILE Filed June so, 1944 5 Sheets-Sheet '2 INVENTORS HENRY f. DUNLAP OHARL'ES E 04;;1/7' 25 L ATT EY Jan.'17, 1961 DUNLAP ET AL 2,968,246

' INVENTORS HENRY FI DUNLAP BYCHARLES fiEHAgUTZEL ATTO Y United States Patent 6 PROJECTILE Henry F. Dunlap and Charles E. Hablutzel, Albuquerque, N. Mex., assignors, by direct and mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed June 30, 1944, Ser. No. 543,007

1 Claim. (Cl. 102-93) This invention relates to sabot projectiles of the type which includes a subcaliber core having substantially full caliber means thereon for supporting and centering the core in a gun barrel and discardable from the core under centrifugal force when the projectile emerges from the gun muzzle. More particularly, the invention has reference to a novel rotary projectile of the type described which is simple in construction, has relatively few parts, is easy to manufacture and has desirable characteristics in operation.

One object of the present invention resides in the provision of a sabot projectile having a subcaliber core and a single sleeve-like sabot-bourrelet unit of plastic or other light weight material mounted on the core and extending continuously from adjacent the nose portion of the core to a point nearthe rear end of the core, the unit being acted upon by the powder pressure in the gun barrel and being releasable from the core under centrifugal force when the projectile emerges from the gun muzzle.

Another object of the invention is to provide a sabot projectile of the character described in which the sabotbourrelet unit is at least partially segmented by longitudinal radial cuts to facilitate breaking and release of the unit under centrifugal force.

Still another object of the invention is to provide a sabot projectile of the character described in which the sabot-bourrelet unit is completely segmented and has a retaining sleeve for holding the segments together on the core while the projectile is in the gun barrel, the sleeve being breakable under centrifugal force when the projectile emerges from the gun muzzle to release the segments.

, A further object of the invention resides in the provision of a sabot projectile having a single sleeve-like sabot-bourrelet unit of substantially full-caliber dimension mounted on a su bcaliber core and having a longitudinal slot to provide a weakened zone to facilitate release of the unit under centrifugal force, and a gas sealing plug mounted on the unit in'the rear end of the slot.

An additional object of the invention is to provide a sabot projectile comprising a subcaliber core having a plurality of segments of light weight material threaded thereon to form a sabot projecting radially from the core, and a metal turning band screwed on the peripheral portion of the sabot and operable to hold the segments together on the threaded portion of the core and to release the segments from the core during flight of the projectile.

These and other objects of the invention may be better understood by reference to the accompanying drawings, in which Fig. 1 is a perspective view of a sabot projectile made in accordance with the invention;

-'Fig. .2 is a perspective view of the sealing plug shown in Fig. 1;

Fig. 3 is a longitudinal sectional view, partly in side elevation, of the projectile shown in Fig. 1;

Fig. 4 is a front view of the projectile;

Fig. 5 is a cross sectional view on the line 5-5 in Fig. 3; 1

Fig. 6 is a longitudinal sectional view of a modified form of the projectile;

. Figs. 7 and 8 are cross sectional views on the lines 7-7 and 8-8, respectively, in Fig. 6;

Fig. 9 is a side elevational view of part of the sabotbourrelet unit shown in Fig. 6;

Fig. 10 is a side elevational view, partly in section, in still another form of the sabot projectile;

Fig. 11 is a longitudinal sectional view of the turning band shown in Fig. 10;

Fig. 12 is a side elevational view, partly in section, of

a modified form of the projectile shown in Fig. 10;

Fig. 13 is a cross sectional view on the line 13-13 in Fig. 12;

Fig. 14 is a rear end view of another form of the projectile;

Fig. 15 is a side elevational view of the sabot shown in Fig. 14, and

Fig. 16 is a side elevational view, partly in section, showing the sabot of Fig. 15 assembled on the core.

Referring to the drawings, the projectile shown in Figs. 1 through 5 comprises a subcaliber steel core 10 having an o-give 11, the cylindrical surface of the core being threaded to a point adjacent the ogive, as shown at 12. An elongated sleeve-like member 13 is screwed on the threaded portion 12 and extends from the rear end of the ogive to the rear end of the core. The member 13 is of substantially full-caliber dimension and is made of a light weight material such as fiber, plastic, or the like. Longitudinal slots 14 are formed in the member 13 and radiate from the inner surface of the member so as to partially segment the member. The radial dimension of the slots 14 depends upon the strength of the material from which the member 13 is made, it being understood that the weakened outer portions of the member adjacent the slots 14 are adapted to hold the segments together while the projectile moves through the gun barrel but are adapted to break under centrifugal force when the projectile emerges from the gun muzzle.

The sleeve-like member 13 forms in effect a sabotbourrelet unit mounted on the core 10, the forward portion of the unit 13 serving as a bourrelet to support and center the core in the gun barrel, and the rear portion of the unit serving as a sabot to support and center the core and also to carry a turning band 15. The band 15 is made integral with the sabot-bourrelet unit 13 and is somewhat greater in external diameter than the unit so that the band is adapted to be engraved by the usual rifling in the gun barrel to impart rotation to the projectile. v

In order to prevent leakage of the high pressure powder gases through the slots 14, we provide sealing plugs 17 on the rear end of the sabot-bourrelet unit 13. Each of the plugs includes a flat head which fits closely against the rear end of unit 13, and a shank 18 which is press fitted in the slot 14, the shank extending from the outer edge of the slot to the threaded portion of the core. The plug 17 may be of brass, copper, or other suitable material. Alternatively, the slots may be filled with sheets of plastic or other material which not only act as gas seals but also prevent sabot distortion upon transmission of torque.

In operation, when the projectile is fired from a gun, the powder pressure acts upon the rear ends of the core 10 and the sabot-bourrelet unit 13, the pressure on the plug heads17 serving to maintain the plugs firmly inposition in the slots 14. By the action of the rifling on the turning band 15, the projectile is rotated as it moves through the gun barrel, but the confining efiect of the barrel on the projectile holds the sabot-bourrelet unit together on the core 10 against the action of centrifugal force. However, when the projectile emerges from the gun muzzle and is released from the confining effect of the gun barrel, the sabot-bourrelet unit 13 breaks apart adjacent the slots 14 under. the action of centrifugal force, whereby the unit 13 is released from the core and the latter proceeds on its trajectory without the aerodynamic drag which would otherwise be imposed upon the core by the unit 13.

With the new construction, the sabot-bourrelet unit may be made of relatively weak light Weightmaterial so that the ratio of the sabot-bourrelet mass to the mass of the core is maintained relatively low,,which is desirable in projectiles'of this type; Because of the sleeve-like form of the sabot-bourrelet unit 13 and'the manner of'maintaining it on the core, the unit is held securely in place on the core during movement of the projectile through the gun barrel. Also, when the projectile emerges from the gun barrel, the centrifugal release of the sabot-bourrelet unit from the core is effected with a relativelylow energy loss and without substantially affecting the flight stability of the core. The sealing plugs 17 not only prevent leakage of the high pressure powder gas through the weakening slots 14, but also strengthen the rear end portion of the sabot-bourrelet unit when it is subjected to the greatest stresses. The sabot-bourrelet unit and turning hand, being integral, may be manufactured expeditiously. Ifdesired, the sabot-bourrelet unit 13 may be made of laminations of lightweight material such as" dilecto, the laminationspreferably being perpendicular, to the axis of the projectile.

Theprojectile shown in Figs; 6 through 91compn'ses a subcaliber core 20 made of steel and having an vogive 20a. Directly to the rear of-theogive, the cylindrical sur-. face ofthecore isthreaded, as shown at 20b; 'A sabotbourrelet unit 21 is screwed on the threaded portion 20b of the core and extends from the ogive to a point ad jacent the rear end of the core. The unit 21, as shown, comprises four longitudinal segments which are fitted closely together on the threaded portion of the core, although it will be understood that any other desired number of segments may be employed. The segments 21 form a sleeve-like sabot-bourrelet unit, the forward por-. tion 22 of which is externally threadedand'serves as the-bourrelet. The rear portion 23 of the unit 2 1 is likewise externally threaded and serves as the sabot, the portions 22 and 23 being separated by a shoulder 24 havingan external diameter somewhat greater thanthe adjacent threaded portions. i

In order to hold the sabot-bourrelet segments 21 together on the threaded portion of the core 2%), we provide a sleeve 26 which is screwed on the course 22 of the bourrelet portion of the unit, the sleeve being tightened against the front face of shoulder 24. Preferably, the. sabot-bourrelet segments 21 are made of a light weight material, such as fabric, plastic, or laminated dilecto having the laminations perpendicular to the projectile axis, and the sleeve 26 is made of a similar light weight material, although it will be understood that metal may be used if desired. As shown, the cylindrical outer surface of sleeve 26 has fiush with the cylindrical surface of shoulder 24.

A turning band 27, which may be madeof copper, is threaded on the course 23 on the sabot portion ofunit 21 and istightened against the rear face at shoulder 24. Theband 27 has an external diameter somewhat greater than that of the shoulder and the sleeve 26, so that the band is adapted to be engraved by the gun rifiing to im-. part rotation to the projectile. To the rear ofthe turnitlg bandaa sealing disk 28, which may be madeof metal, is fitted closely on the core and engages the rear face of j'the sabot-bourrelet unit 21 to prevent leakage of the. hish P s ur aw -s e t ss flias qt lwllrts st. s'giileritsf When the projectile is fired from agun, the sleeve 26 and turning band 27 act .to hold the sabot bourrelet segments 21 together on the core 20 as the pro ect le moves through the gun barrel. When the projectlle emerges from the gun barrel and is released from the confining effect of the barrel, the centrifugal force incident to its rotation causes thesleeve 26 and turning band 27 to break apart and thereby release the segments 21 from the core, the disk 28 being then moved off the rear end of the core by the air pressure on the disk. It will be understood that the threads 20b, 22 and 23 are in such a direction that the parts mounted thereon are tightened onthe threads-bythe. rotation imparted to the projectile through the turning band.

Referring to Figs. 10 and '11, the projectile there shown comprises a sub-caliber core 30 having an ogive 30a, the cylindrical portion of the core being threaded as shown at 30b. A substantially full caliber sabot-bourrelet unit 31 is threaded on the cylindrical portion of the core and is'in the form of a sleeve extending from the ogive to a point adjacent the rear end'of the core. At its rear end portion, the unit31'is reduced and externally threaded, as shown at 32, anda turning band 33, made of copper or the like, is threaded on the-reduced portion 32 and tightened against the shoulder at the front end of the reduced portion.

The sabot-bourrelet unit 31 is made of a light weight material, such as fiber, plastic, or the like, the material having atensile strength such that the unit is adapted to break apart under the centrifugal force when the projectile emerges from the gun barrel, inthe absence of weakening cuts-or segmentation.- It-will be understood that the turning band 33, due-to its-own mass, will fracture under the centrifugal-force when the 'projectileemerges from the gun muzzle, thereby permitting the unit 31 to break apart-as-deseribed. Thecore 30 is thus released from the sabot-bourrelet unit and the turning band and proceeds on its trajectory. We have found that molded macerated fabric phenolic may be used to advantage for the sabot-bourrelet unit 31, the material being molded in such a way that the finished bourrelet machined from it has two zones of tensile strength weakness apart.

The projectile shown in Figs. 12 and 13 is similar to that. shown in Figs. 10 and 11, except that the sabot-- bourreletunit 31a-is provided with longitudinal slots' 35 radiating-from the inner 'surfaceof the unit but terminatingshort of its outer surface, so as to partially. segmenttheunit. The slots 35 are closely packed with a fiber filling 36 so as to prevent leakage of the high pressure powder gases through the slots and also to prevent sabot distortion upon transmission of torque. It will be understood that the slots 35 provide weakened zones in the sabot-bourrelet unit to facilitate fracturing of the unit for release from the core under centrifugal force when the projectile emerges from the gun muzzle.

The projectile shown in Figs. 14, 15 and 16 comprises asubcaliber core 40, the rear end portion of which is externally threaded as shown at 40a. A full caliber sabot 41 is-screwed on the threaded portion 40a and comprises a plurality of segments 42 fitted closely together. and held on the core by a turning band 43 threaded on the peripheral portion of the sabot. The sabot segments 42 are made of light weight material, such as plastic, fiber, or thelike, and project radially from the cylindrical surface of the core for a substantial distance for supporting and centering the core in thegun barrel and carryingthe turning band 43, which is-made of copper: or other suitable metal. The projectile is preferably providedwith a suitable bourrelet (not shown) mounted on the core 40 in front of the sabot. ent that when the projectile is. -fired from a gun, the turning band 43, due to its own mass and that of thesabot'.

segments, will break under the action of centrifugal force when the P e tilemersestfrom -the gun. barrel, there,-. byreleasing the sabot segments.

It will be appanl.

It will be apparent that the illustrated embodiments of the invention are of simple construction, may be easily manufactured and assembled, and have relatively few parts. The rotating band may be molded or threaded on the sabot-bourrelet unit, and the latter may be molded or threaded on the projectile core. In this connection, if the sabot-bourrelet unit is molded on the core, the manufacturing problems are more simple than in a machined connection between the sabot-bourrelet unit and the core. The mass of the sabot-bourrelet unit may be made quite small, thus allowing the attainment of higher velocities for a given projectile mass than with any other type of sabot and bourrelet. Since the sabot-bourrelet fragments are lighter than would be the case if steel or other metal were employed, the range of these fragments upon centrifugal release from the core is less than for corresponding steel fragments, and the danger from these fragments to personnel in the immediate vicinity of the gun is correspondingly reduced.

Since the plastic or other light-weight sabot-bourrelet unit is exposed to the powder gases, the compressive strength of the sabot-bourrelet material should be greater than the maximum powder pressure, in order to avoid crushing at the rear portion of the sabot-bourrelet unit. For modern phenolic formaldehyde plastics, the compressive strength is about forty thousand pounds per square inch, while most modern guns have maximum pressures somewhat less than this. Attention is directed to the fact that most plastics, particularly the laminated type, are not isotropic. This must be considered in the sabot-bourrelet design, so that the high stresses are applied in the direction of maximum strength of the plastic.

In the practical design of plastic or other light-weight sabot-bourrelet units, it has been found desirable to fill the longitudinal weakening slots, either by inserting plastic or metal strips or by closely fitting the segments and holding them together with an over-all sleeve. Otherwise, there is a tendency toward relative motion between the segments during transmission of torque, which may result in failure in the gun. Filling of the slots, at least for part of their lengths, is necessary also to effect the gas seal. As pointed out in connection with the projectile illustrated in Figs. 10 and 11, an all-plastic sabotbourrelet unit may be employed which does not have the weakening slots. It has been found that such a unit will release satisfactorily from the core even though the calculated bursting tensile stress to which the unit is subjected is considerably below the supposed strength of the plastic.

It is to be understood that the various forms of the projectile disclosed herein are susceptible of various modifications within the scope of the invention. In the following claim, the term plastic is intended to include equivalent light weight materials, such as fabric, wood, and the like.

We claim:

In a sabot projectile having a subcaliber projectile core and a turning band, a single sleeve-like sabot-bourrelet unit of plastic material mounted on the core and extending continuously from adjacent the nose portion of the core to a point near the rear end of the core, said unit projecting radially from the core a substantial distance for supporting the core in a gun barrel and having a longitudinal slot to provide a weakened zone, the unit supporting the turning band on the sabot portion of the unit and being releasable from the core during flight of the projectile, and a gas sealing plug having a tongue portion fitted closely in the rear end of said slot and having a face portion seated against the rear end of the core.

References Cited in the file of this patent UNITED STATES PATENTS 123,828 Jones Feb. 20, 1872 132,903 Dana ,Nov. 12, 187

FOREIGN PATENTS 131,034 Great Britain Aug. 21, 1919 46,057 Sweden Nov. 5, 1919 784,108 France Apr. 23, 1935 801,218 France May 16, 1936 804,237 France July 27, 1936 704,406 Germany Mar. 29, 1941 

